Prosthesis infections are one of the most feared reasons for failure of a prosthesis. With specific reference to hip prostheses, these infections are a fairly frequent occurrence with a percentage varying between 0.5% and 6% of cases. The percentage of infections increases in the event of re-implants or in the presence of risk factors such as previous surgery, local hematomas, intercurrent infectious diseases, local or general bone diseases, impaired immunity system, etc.
One method of curing the infection, defined as a two-step treatment, consists of a first step in which the infected prosthesis is removed, since the probability of mere conservative antibiotic treatment being successful is extremely limited, and a second step in which a new prosthesis is implanted once all the infection has been eliminated from the patient's tissues.
In order to maintain the space necessary for the new prosthesis implant and to cure the infection, the applicant has developed special prostheses for temporary use, also called temporary spacers, which release pharmaceutical and/or therapeutic products and permit articular mobility.
These spacers are the subject of the Italian patent no. IT-1278853 and of the European patent no. EP-1274374 in the name of the same applicant and incorporated herein by reference for all purposes.
The international patent application WO-2007/099232 describes a temporary spacer which comprises a semispherical (hemispherical) head which is inserted in the corresponding joint and which can be separated from and attached to a rod to be inserted in the bone bed remaining from the previous implant. With the spacer described in WO-2007/099232, it is possible to combine a rod with different sized semispherical heads in order to adapt to the anatomy of the patient's joint. The connection between the semispherical head and the rod is achieved by means of corresponding truncated cone areas.